Lectures on the blood and on the changes which it undergoes during disease : delivered at the College of France in 1837-8 / by F. Magendie.

  • Magendie, François, 1783-1855.
Date:
1839
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on the blood and on the changes which it undergoes during disease : delivered at the College of France in 1837-8 / by F. Magendie. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    and animal substances; administers them right or wrong, without considering for a moment the cause of the disease, and without a single clear idea on the why and wherefore of his conduct. You may prove to him, as you will, that this or that substance is in- significant, useless, or even hurtful; little will he regard your ex- postulation. And why should he, when, by readiness in prescribing a monstrous farrago of drugs, he knows he shall acquire the reputation of being profoundly versed in the materia medica, of being a man of immense resources, 6fC. ? Such, Gentlemen, has ever been empiricism. We were speaking of the viscidity requisite for the circulation of the blood through our organs. Now, here is the blood of an individual who had an attack of hemoptysis, and was bled freely for it. You know well what I think of that remedy,—worse, per- haps, than the disease. Be that as it will, you may perceive that this blood is very slightly viscous; I, in consequence, presume that further mischief will occur. We shall see if my presumptions are realised. We have no instruments to measure the viscidity of fluids; we are, therefore, instead of having an accurate and rigorous estimate of that of the blood, reduced to simple conjectures. I consider that the discovery of any method of measuring it with exactness would be a most valuable acquisition. Meanwhile, we will do what we can to determine it with the areometer. There is further proof that a certain share of viscidity is an essential requisite for the healthy circulation of the blood. If you bleed an animal several times, and replace the blood withdrawn with water, exhalation and effusion into the cavity of the pleura will follow, and, subsequently, into the peritoneum. Now, you have done no more than diminish the viscidity of the blood, by adding a little water to it. But, on the other hand, if you iry the converse experi- ment, and augment its viscidity beyond its natural term, the cir- culation ceases altogether, in consequence of the affinity between the molecules of the blood being rendered too great. The molecules adhere to the walls of the vessels, and impede the circulation, just as blocks of ice, stuck to the banks of canals, or rivers, interrupt the course of their streams. Hence there must be diseases origina- ting in excessive viscousness of the blood. You remember the experiments we made to exemplify this question. We added a viscid matter, innocuous in itself, crUmj for example,—to some water, and, after colouring the fluid, injected it into the jugular vein of an animal. So long as the injection traversed the large venous trunks no disorder was occasioned ; but once it had arrived through the pulmonary artery, amongst the minute ramusculi of the lung, its degree of viscidity ceased to be in just proportion to the capacity of the tubes. The consequence was, that the circulation almost instantly stopped, and, as the en cepnalon no longer received the necessary excitement of arterial blood, its functions ceased, and the animal'quickly perished TIip autopsy was immediately made, and, on incising the pulmonary